One image sticks in the mind of many Iranians who remain undecided on whether to vote in Friday's presidential election. It is of Neda Agha-Soltan, a young woman whose death was captured on amateur camera and circulated around the world in 2009, encapsulating a nation's struggle for freedom in the aftermath of the last election, which many believe was rigged.

"These days, her image keeps coming back to my mind," a Tehrani citizen said via online chat on Facebook. "Am I betraying her if I vote? I don't know, but many of my friends are saying we won't achieve anything by simply boycotting the election."

To vote or not to vote for Hassan Rouhani, the sole reformist-backed candidate standing in the race, is the dilemma shared by hundreds of thousands of people who lost faith in the fairness of Iranian polls.

For families who lost loved ones in the aftermath of the 2009 election, the buildup to the vote is adding salt to the wounds. At least 100 protesters are believed to have been killed in the protests.

Unlike Neda, whose death resonated globally, prompting world leaders to comment and inspiring films and books, the identities of a large number of those who lost their lives remain unfamiliar to Iranians.

The Iranian journalist Masih Alinejad, currently exiled in Oxford, has devoted the past four years to identifying the families of the lesser-known victims and documenting details of their deaths through interviews with family and friends.

She has catalogued details of 56 dead protesters. "These are the only people whose families have dared to speak out," Alinejad told the Guardian. "But I'm sure there are dozens more who were killed and we haven't even heard of their names even today."

The human right group Amnesty International said on Wednesday that Iranian authorities had once again stepped up their clampdown on activists and campaigners before the election. Journalists, lawyers and members of Iran's religious and ethnic minorities had been harassed, Amnesty said.

"The escalation in repression is an outrageous attempt by the Iranian authorities to silence critics ahead of the presidential election," said Amnesty's Middle East and North Africa director, Philip Luther. "The surge in recent violations underlines Iran's continued and brazen flouting of human rights standards through its persecution of political dissidents and betrays the glaring absence of a meaningful human rights discourse in the election campaign."

Casualties of the 2009 protests

Profiles by Masih Alinejad

Shabnam Sohrabi The 34-year-old was killed in December 2009 when a black vehicle ran her down. Her mother initially feared speaking up about her daughter's death, but broke her silence and talked to the Where Is My Vote website. "Shabnam had a strong body; I cannot imagine her being crushed under the wheels of a police vehicle," she said.

She explained the process of collecting her daughter's body. "I looked everywhere, including all the hospitals. I finally discovered that she had been taken to Rasoul-e Akram hospital in Tehran, but there were no signs of her there and nobody explained why. After 20 days we received a phone call saying that we could collect her body from the Kahrizak morgue and bury her."

Kianoosh Asa A petrochemical engineering student at the University of Science and Technology in Tehran. Asa, 25, of Kurdish origin, went missing after attending a demonstration on 15 July 2009. Ten days later his body was delivered to the coroner's office and his family were informed. Kianoosh Asa's family published an open letter to the head of the judiciary and demanded an investigation into his death. "Eyewitnesses have informed us that Kianoosh was seen to have received a bullet wound on one side of his body. However, in the coroner's office his body was seen to bear traces of another bullet wound in his neck. The disturbing question is who was behind the second shot," they wrote.

Maryam Soudbar Atbatan A 21-year old university student from Karaj who died at home after being beaten on the head with a truncheon during a demonstration in Tehran on 20 June 2009. Her family were coerced into silence, but three years later her father spoke out. "We were worried for our other children's safety. That is why we kept her case in our heart, but did not talk about her. Maryam went to university as usual on 20 June 2009. She was in good health and had no medical complaints. She returned home and died in her room that very night," he said.

"I don't have any idea why they beat my daughter. After she died, her friends told us Maryam had been bashed on the head with a truncheon and did not feel well. Her friends had helped her to her feet and she had felt better. When she returned home, she did not tell us what had happened. During the night she died in her room."

Hamid Hossein Beik Araghi The state-run Keyhan newspaper and Fars news agency described Araghi as a member of the Basij militia. His mother, Fatemeh Sarpariyan, denied the allegation. His family were shown photographs to identify his body. "His face was full of blood, his front teeth were broken and one side of his face was bruised; he had been shot in the chest and all the pictures were full of blood. For me, his mother, his photos were unbearable to look at and I fainted."

Ali Hassanpour A married father of two children aged 14 and 21. He was shot in the face and died on Azadi Square during demonstrations on 15 June 2009 after helping another person who had been injured. His body was handed over to his family for burial 104 days later. A picture of his body covered with blood and lying on the ground among the protesters was published in the media on the day of the incident.

His wife, Ladan Mostafaei, said that when she showed her husband's photo to the authorities they denied any knowledge of him. "I have told the judicial authorities that, according to countless witnesses, my husband was shot from the rooftop of the 117 Battalion of Ashura Basij building. The arms experts of the judicial authorities have confirmed that a Kalashnikov was the rifle used to kill him."

Hossein Akhtarzand A 32-year-old resident of the city of Isfahan who participated in the protests and was beaten and killed by the militia. A commander in the special unit in Isfahan reported that Akhtarzand had fallen from the third floor of a building while under the influence of drugs. In the first days of post-election violence, witnesses posted photos of Akhtarzand online showing that he had been badly beaten on his left arm and left leg and the right side of his back, and had a deep laceration down his right-hand side (as certified in the sheet provided by the coroner).

Akhtarzand's family remained silent for two years before his brother, Javad, exposed the killing of his brother by the authorities. "In the city of Isfahan, as in many other cities, protests flared up against the June 2009 elections. Owing to the heavy-handed approach adopted by the officials, people ran for their lives and Hossein tried to hide in a clinic building. However, he was discovered by the security agents and tossed down from the top of the building, the claim being that he had jumped of his own accord."